The present invention relates to a method of staring an engine for automatically starting the engine under a control of a starting system of the engine including a starter protection device, performed by a vehicle mounted microcomputer, and an apparatus therefor.
FIG. 3 shows a construction of a conventional engine atarting system such as disclosed in Japanese Patent Publication No. 10187/1985 and FIG. 4 is a flow chart showing an operation of a microcomputer used therein.
In FIG. 3, a reference numeral 1 depicts a vehicle mounted battery and 2 an engine key switch having an OFF terminal 2a for cutting a power source off, an ACC terminal 2b for supplying power to various accesaries of the vehicle and an IG terminal 2c for supplying power to various functional devices of the vehicle such as an ignition system.
In FIG. 3, a car radio device 3 which is one of the accesaries is connected to the ACC terminal 2b of the key switch 2. The ignition circuit 4 is shown an a typical example of the functional devices and connected to the IG terminal 2c of the key switch 2.
A hand brake switch 5 produces an on or off signal according to an operation thereof, which is supplied to the microcomputer 9.
A neutral sensor 6 produces an on or off signal according to a position of a change lever, which is also supplied to the microcomputer 9. An engine revolution sensor 7 detects an engine revolution and provides an output signal indicative of the latter which is supplied to the microcomputer 9.
A coolant temperature sensor 8 for detecting temperature of coolant such as water regulates a control of the automatic engine starting, an output signal of which is also supplied to the microcomputer 9.
The microcomputer 9 performs various operations according to predetermined programs, and, when it receives a signal indicative of an activation of the IG terminal 2c of the key switch 2, it checks signals from the hand brake sensor 5 and the neutral sensor 6. When the checks indicate incomplete engine starting conditions thereof, the microcomputer 9 provides an incomplete alarm signal.
When the checks indicate complete engine starting conditions, the microcomputer 9 provides a power supply start signal so that a power supply to an engine starter for a unit time necessary to start the engine is repeated at a predetermined interval and, when a completion of engine start is decided by the signal from the engine revolution sensor 7, the microcomputer 9 provides a power supply termination signal. The microcomputer 9 regulates the repetition times of the power supply to the starter, the unit time and the interval on the basis of the signal from the coolant temperature sensor 8. When it is impossible to start the engine even if the repetition times becomes a predetermined value, the microcomputer 9 stops to supply power to the starter and provides an impossible alarm.
An R-S flip-flop 10 which serves as a holding means is set by the power supply start signal from the microcomputer 9 and holds the set state to maintain a hold signal until it is reset upon the power supply termination signal therefrom.
A starter circuit 11 includes a starter motor and serves to supply power to the latter for a time period in which the hold signal is kept produced by the flip-flop 10.
An alarm 12 provides a continuous alarm signal indicative of incomplete condition for engine starting according to the incomplete condition alarm signal from the microcomputer 9 which is stored in a memory provided in the alarm 12.
A start impossible alarm 13 includes a memory for storing the impossible signal from the microcomputer 9 and provides a continuous alarm thereby.
The microcomputer 9 performs various other controls for various systems such as fuel injection system, ignition timing system, etc., than these mentioned above. Practically, the microcomputer 9 performs the engine starting control by utilizing time periods which are not used by these system controls.
The engine starting control will be described in more detail with reference to FIG. 4. When the key switch 2 is turned from the OFF terminal 2a to the ACC terminal 2b, the car radio 3 is supplied power from the battery 1 through the ACC terminal 2b and therefore the radio 3 can be turned on by a switch thereof. At the same time, other accesaries are also supplied power. However, since the IG terminal 2c is still opened, there is no power supply to the various function devices of the vehicle.
Then, when the key switch 2 is turned from the ACC terminal 2b to the IG terminal 2c, the function devices such as the ignition circuit 4 are supplied with power through the IG terminal 2c while the power supply to the accesaries through the ACC terminal 2b is maintained. Therefore, the microcomputer 9 becomes operative.
Upon the turning of the key switch 2 from the ACC terminal 2b to the IG terminal 2c, the microcomputer 9 starts to operate to perform the automatic engine starting from a key switch on step 101 and to a selfchecking step 102, as shown in FIG. 4. In the step 102, abnomalities of basic operation of the microcomputer 9 and its memories are checked by itself according to a predetermined self checking program. When there is any abnomality, the operation is shifted to an incomplete alarm step 105 to produce an incomplete alarm signal from the incomplete alarm 12.
When the check in the step 102 indicates no abnomality of computer operation, the operation is shifted to a hand brake decision step 103. In the step 103, it is checked from the signal from the hand brake sensor 5 whether or not a hand brake is effective, and, if no, the operation is shifted to the incomplete alarm step 105 to produce the incomplete alarm signal from the alarm 12.
On the other hand, the check in the step 103 indicates that the hand brake is effective, the operation is shifted to a neutral decision step 104.
In the step 104, it is checked according to the signal from the neutral sensor 6 whether or not the position of change lever is neutral. If no, the operation is shifted to the step 105 to produce the alarm signal from the alarm 12.
If yes, that is, if the operational function of the microcomputer 9 is normal, the hand brake is effective and the change lever is in neutral position, indicating a complete engine starting condition, the operation is shifted to a coolant temperature step 106 in which a temperature signal TW is obtained according to the signal from the coolant temperature sensor 8, and then the operation is shifted to a function setting step 107.
In the step 107, by using the coolant temperature TW as a variable, a starter power supply time T.sub.1 =f.sub.1 (TW), the interval time T.sub.2 =f.sub.2 (TW) and the number of starter power supplies K=f.sub.3 (TW) are set. In this case, the times T.sub.1 and T.sub.2 depend upon the coolant temperature, the longer the higher, and are set about 5 seconds and about 10 seconds, respectively.
The number K of power supplies is a stepwise function of TW and is an interger reverse proportional to TW. The number K is set in a range from 3 to 5.
The operation of this conventional device will be described for a case where the starting condition is incomplete under conditions that the starter power supply time T.sub.1 is 5 seconds, the interval T.sub.2 is 10 seconds and the number K of power supplies is 3. A T.sub.1 timer of 5 seconds is started in a timer start step 108 and the operation is progressed through a T.sub.1 timer up decision step 109 to a starter power supply on step 110 in which a power supply start signal is supplied to the R-S flip-flop 10 to set the latter the holding signal of which is used to start a power supply to the starter circuit 11 and a loop from an engine start decision step 111 to the T.sub.1 timer up decision step 109 is repeated.
When the engine is not started with this operation within the starter power supply time of 5 seconds, an output of the step 109 is turned from NO to YES and the operation is shifted to a starter power supply off step 114. In the step 114, a power supply termination signal is supplied to the R - S flip-flop 10 to reset the latter to thereby remove the holding signal and stop the power supply to the starter circuit 11.
Then, the operation is shifted to a T.sub.2 timer start step 115 to start the 10 seconds operation of the timer T.sub.2 and a return loop is repeated in a T.sub.2 timer up decision step 116.
After the T.sub.2 time period of 10 seconds lapses, the decision made in the step 116 is turned from NO to YES and the operation is shifted to a subtraction step 117 in which a subtraction K=K-1 is performed to change the number from 3 to 2, and the operation is returned through a number decision step 118 to the T.sub.1 timer start step 108.
When the engine can not be started even when the same operation is repeated three times, the decision made in the step 118 is turned from NO to YES and the operation is shifted to an impossible alarm step 119 to provide an impossible alarm from the impossible alarm 13 in addition to the incomplete alarm from the incomplete alarm 12.
As to a case where the engine is started by a first power supply to the starter, the operation is performed from the steps 101 to 113 similarly, without the routine from the steps 114 to 119.
In the conventional system mentioned as above, the device is actuated by turning the engine key switch from the OFF terminal to the IG terminal. Therefore, there may be a case where a power supply to the starter motor is reduced due to an increase of power consumption of various accesaries connected to the ACC terminal, causing the starting operation difficult. Further, since the operation of the key switch is somewhat different from a conventional engine starting, there may be some troubles for untrained drivers.
Further, the power supply to the starter circuit is started after all of the checks for engine starting show complete conditions and continues until the decision of complete engine start or the provision of the start impossible alarm, it is impossible to terminate the power supply when a malfunction occurs after the checks.
In addition, since the holding means, flip-flop, provides instructions to start and to stop the power supply to the starter, it is impossible to control an excitation current of the starter motor by effectively utilizing the microcomputer, so that th conventional device is not suitable to obtain a starter device having a starter control. There have been various protective devices for protecting, for example, a starter against the problems mentioned above. However, these protective devices require control circuits specialized therefor, making them unsuitable to perform a control covering all of the starting system including automatic engine starting and protection of the starter by means of a microcomputer.